<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <!-- 连接后等于目标字符串的字符串对 -->
    <script>
      var numOfPairs = (nums, target) => {
        let res = 0
        let len = nums.length
        for (let i = 0; i < len; i++) {
          // 若开头就对不上，直接进行下一个的判断
          if (target.indexOf(nums[i]) !== 0) continue
          for (let j = 0; j < len; j++) {
            // 排除i===j的情况
            if (i === j) continue
            if (`${nums[i]}${nums[j]}` === target) res++
          }
        }
        return res
      }
      console.log(numOfPairs(['777', '7', '77', '77'], '7777'))
    </script>
  </body>
</html>
